Endoscopes are presently used for diagnostic and therapeutic purposes. There are many different uses for endoscopes, and frequently the endoscope design is varied, depending on its use, to optimize the performance of the endoscope for its intended purpose. As such, there are specific endoscopes for the areas in which they are used. For example, there are upper endoscopes for examination of the esophagus, stomach and duodenum, bronchoscopes for examining the bronchi, laparoscopes for examining the peritoneal cavity, arthroscopes for examining joint spaces, angioscopes for examining the blood vessels and heart, colonoscopes for examining the colon, sigmoidoscopes for examining the rectum and sigmoid colon, and cystoscopes for examining the urethra and bladder.
The endoscope may include one or more diagnostic or treatment devices, such as tubings for water, air and biopsy suction; a viewing device, a temperature sensor, a heating probe, an ultrasonic sensor, a laser catheter or the like. The tubings inside the endoscope must be capable of bending or flexing without kinking or collapsing as the endoscope is moved through the body.
In the field of endoscopes, a conventional endoscope 5, shown in FIG. 1, has an insertion tube 17 connected at its proximal end 19 to a handle or control body 20. The insertion tube 17 is adapted to be inserted into a patient's body cavity to perform a selected therapeutic or diagnostic procedure. The insertion tube 17 contains an imaging system having optical fibers or the like extending along the length of the insertion tube and terminating at a viewing window 22 in the insertion tube's distal end 18. The imaging system conveys an image from the viewing window 22 to an eyepiece 23 on the control body 20 or to a monitor (not shown), so the user can see into a selected body cavity during an endoscopic procedure. The endoscope 5 is described in greater detail in U.S. Pat. No. Re 34,110 and U.S. Pat. No. 4,646,722, which are incorporated herein by reference.
Endoscopes are limited in utilising additional equipment by the number and diameter of the working channels in which it incorporates.
Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscope. These lenses let the physician focus on the inner surfaces of the urinary tract. Some cystoscopes use optical fibres (flexible glass fibres) that carry an image from the tip of the instrument to a viewing piece at the other end. Cystoscopes range from paediatric to adult and from the thickness of a pencil up to approximately 9 mm and have a light at the tip. Many cystoscopes have extra tubes to guide other instruments for surgical procedures to treat urinary problems.
There are two main types of cystoscopy, flexible and rigid, differing in the flexibility of the cystoscope. Flexible cystoscopy is carried out with local anaesthesia on both sexes, typically with a topical anaesthetic. Rigid cystoscopy can be performed under the same conditions, but is generally carried out under general anaesthesia, particularly in male subjects, due to the pain caused by the probe.
One of the complications requiring observation and treatment within the urinary tract is the occurrence of kidney stones. A kidney stone, also known as a renal calculus (from the Latin rēnēs, “kidneys”, and calculus “pebble”), is a solid concretion or crystal aggregation formed in the kidneys from dietary minerals in the urine.
Urinary stones are typically classified by their location in the kidney (nephrolithiasis), ureter (ureterolithiasis), or bladder (cystolithiasis), or by their chemical composition (calcium-containing, struvite, uric acid, or other compounds). About 80% of those with kidney stones are men.
Kidney stones typically leave the body by passage in the urine stream, and many stones are formed and passed without causing symptoms. If stones grow to sufficient size (usually at least 3 millimeters (0.12 in)) they can cause obstruction of the ureter. Ureteral obstruction causes post-renal azotemia and hydronephrosis (distension and dilation of the renal pelvis and calyces), as well as spasm of the ureter. This leads to pain, most commonly felt in the flank (the area between the ribs and hip), lower abdomen, and groin (a condition called renal colic). Renal colic can be associated with nausea, vomiting, fever, blood in the urine, pus in the urine, and painful urination. The diagnosis of kidney stones is made on the basis of information obtained from the history, physical examination, urinalysis, and radiographic studies. Ultrasound examination and blood tests may also aid in the diagnosis.
When a stone causes no symptoms, watchful waiting is a valid option. For symptomatic stones, pain control is usually the first measure, using medications such as nonsteroidal anti-inflammatory drugs or opioids. More severe cases may require surgical intervention. For example, some stones can be shattered into smaller fragments using extracorporeal shock wave lithotripsy. Some cases require more invasive forms of surgery. Examples of these are cystoscopic procedures such as laser lithotripsy or percutaneous techniques such as percutaneous nephrolithotomy. Sometimes, a tube (ureteral stent) may be placed in the ureter to bypass the obstruction and alleviate the symptoms, as well as to prevent ureteral stricture after ureteroscopic stone removal.
Currently, if a patient presents with a kidney stone and requires a stent to be placed in their ureter, they must be sent for a rigid cystoscopy which involves general anesthetic with associated risks and costs. Flexible cystoscopes allow ureter visualization and access via guide wire, but minimal working channel diameter prevents stent placement and the relieving of patient discomfort.
Endoscopes must be adequately cleaned and sterilized between each use to ensure that disease is not transmitted from one patient to another. For example, upper endoscopes, colonoscopes, angioscopes and sigmoidoscopes all come in contact with the blood and other body fluids which are capable of transmitting diseases from one person to another. Even though the endoscopes are cleaned between each use, often using chemicals, such as glutaraldehyde, complete sterilization is not ensured. Some body particles may lodge in a crevice of the endoscope and not be contacted by the sterilization fluid.
Optimization of intrabody medical equipment for such therapeutic and diagnostic procedures has resulted in sterile, inexpensive disposable components that are used alone or with non-disposable equipment.
There are many examples of disposable endoscopic sheath assemblies currently in common use today and variations of the process described in the above paragraphs are commonly used and are well known in the prior art. The substantial prior art in this area can be referenced in the cited patents of this document.
Disposable endoscopic sheath assemblies are primarily used to cover the endoscope insertion tube and protect it from contaminating a patient during use. Accordingly, the sheath assemblies alleviate the problem and cost of cleaning and sterilizing the insertion tube between endoscopic procedures. The sheaths and endoscopes are usable in medical applications and also in industrial applications, such as visually inspecting difficult to reach areas in an environment that could damage or contaminate the endoscope.
The sheath can be made from an inelastic polymer, such as PVC, acrylic, polycarbonate, polyethylene terephthalate or other thermoplastic polyesters, or can be made from an elastomeric material. Both materials presently have advantages and disadvantages. Inelastic materials allow for thin-walled medical components that exhibit high strength and visible clarity. Using inelastic materials, the sheath can be formed with a thin wall (measuring 0.003 inches or less).
Inelastic materials, however, have a number of disadvantages. Tight-fitting sheaths formed from inelastic materials may overly restrict bending when used with flexible insertion tubes. The insertion tube combined with the tight-fitting, inelastic sheath can only bend over a limited radius. If bent further, the sheath will either buckle, in the case of a thick-walled sheath, or the sheath material will become taught, in the cause of a thin-walled sheath, preventing the insertion tube from bending further. Consequently, if the inelastic sheath is to be used in combination with a flexible endoscope, the sheath is typically either baggy or must contain bending features, such as accordion-like baffles or the like, to allow the insertion tube to sufficiently bend. Both baggy sheaths and these additional bending features add to the cross-sectional size of the sheath during use, which may result in additional pain or discomfort to the patient.
Conventional elastic sheaths have been developed and used with imaging devices such as endoscopes to overcome the drawbacks associated with the inelastic sheaths described above and to provide additional benefits. As an example, conventional elastic sheaths are designed so the sheath will easily bend with the insertion tube without substantially affecting the insertion tube's bending characteristics. The elastic sheath can be designed to closely or tightly cover the insertions tube while still being able to bend with the insertion tube, so the elastic sheath does not need additional bending features.
Elastic materials, however, also have some disadvantages. First, conventional elastic sheaths are manufactured by extruding elastomeric material. The extruded elastic sheaths, however, have manufacturing limits that restrict the minimum wall thickness of the sheath, particularly for sheaths having small internal diameter. Efforts toward manufacturing such a sheath have typically resulted in the extruded material collapsing or wrinkling and adhering to itself during the process. As a result, the extruded elastic sheath must be made with a relative thick wall (i.e., greater than 0.006 inches). The thicker the sheath wall, in a tight-fitting sheath, the greater the resistance to bending.
Tight fitting, elastic sheaths can also be complex and expensive to install onto the insertion tube. The elastic materials commonly used to manufacture the sheath have high friction characteristics. As a result, it can be difficult to insert the insertion tube into the tight-fitting sheath because the insertion tube binds on the inner wall of the sheath. One solution is to make the sheath with a diameter considerably larger than the insertion tube, so the sheath is baggy when installed on the insertion tube. Baggy sheaths, however, are undesirable in many endoscopic procedures because the sheath can be twisted, bunched, or misaligned relative to the insertion tube during the procedure. The baggy sheath can also increase the diameter of the sheathed insertion tube, which can increase pain or discomfort to the patient.
In the design of intra-body medical devices and accessories, including optical and non-optical devices, there is a need for components having the benefits of both elastic and inelastic materials while, at the same time, avoiding the disadvantages associated with these materials. As an example, there is a need for an elastic component that can be manufactured with both a thin wall and a small internal diameter. There is also a need for a small diameter, elastic sheath that can be quickly and inexpensively installed and used on a flexible insertion tube. Other medical devices and accessories would also benefit by such inexpensive, elastic, thin-walled components.
Presently, a limiting constraint in designing endoscopes is that the diameter of the endoscope must be less than the diameter of the body cavity through which the endoscope must travel. And the ability of a patient to tolerate an endoscope is related to its diameter. An endoscope for use in the stomach cannot be larger in diameter than the esophagus. Endoscopes for use in the gastrointestinal tract cannot be larger in diameter than the rectum, colon or large intestine, depending upon the length which the endoscope is inserted into the digestive tract. Angioscopes for examining the blood vessels and heart must be smaller in diameter than the smallest blood vessel through which the angioscope must pass.
The medical diagnostic and treatment which can be performed using an endoscope may be limited by its diameter. For example, the diameter of the endoscope may not be sufficiently large to permit both an ultrasonic probe and a video probe to be located within the same endoscope. Similarly, the physician may desire to have an endoscope which includes a video probe, a biopsy channel and graspers for removing tissue viewed by the video probe. However, the diameter of the endoscope may be limited to a size smaller than that required to include a grasper, a biopsy channel and a video probe in the same endoscope. The physician may wish to have a temperature sensor, heater probe, multiple-arm grasper, wash channel, forward viewing video probe, side viewing video probe, binocular lens, wide angle lens, ultrasonic sensors, ultrasonic heating devices, lasers, micrometers or the like for use alone or in combination with each other in diagnosing or treating a patient. Unfortunately, the diameter of the body cavity through which the endoscope must pass may not be sufficiently large to permit an endoscope to be routinely passed which is sufficiently large to accommodate more than one or two of the possible diagnostic and treatment devices which might need to be used.